MICROMORPHOMETRY OF SOIL AGGREGATES UNDER DIFFERENT RICE CROPS MANAGEMENT SYSTEMS

For a long time, people have tried fo find an index to qualify the soil structure and, for this purpose, the study of soil aggregates digital images can be a promising procedure. The aim of this study was to characterize micromorphometrically aggregates of a typical Dystrudept soil under the influence of different rice crops management systems. The cultivation systems used were: conventional system with sowing in flooded area, sowing in upland area, and crop rotation with maize and rice, in a triennial cycle. Aggregates were collected at 0-0.20 m depths, being used those retained at diameters of 9.52-4.76 mm and 4.76-2.00 mm, with a standard set of sieves. The aggregates analyses were carried out with the aid of digital images from a scanner (300 dpi) over a total of 100 aggregates disposed over a tray with uneven holes. The images were subsequently analyzed by using the Quantporo program and the aggregates features evaluated were: area, perimeter, roughness, and aspect. Data obtained from soil aggregates micromorphometric analyses were submitted to the frequencies distribution analyses, Chi-square test, and Spearman's nonparametric correlation test. According to the main micromorphometric features of smaller size aggregates (2.00-4.76 mm), it was possible to conclude that, under the conventional system, aggregates were predominantly smaller, roundish, and smoother.